(1) Field of the Invention
The present invention relates to the field of cavitation suppression for sonar arrays, and more particularly to suppression of the cavitation that often occurs between closely spaced transducers operated at high source levels.
(2) Description of the Prior Art
It is well known that the interaction between adjacent transducers in a sonar array can produce cavitation due to acoustic effects alone. Cavitation is the phase change of water from liquid to vapor induced by a pressure drop in the water. The ideal inter-transducer spacing for an array of transducers disposed within a towed Variable Depth Sonar (VDS) needs to be a distance greater than or equal to one-half of the operational wavelength of the sonar in order to minimize acoustic interactions between adjacent transducers. However, low-frequency (and hence long wavelength) sonar systems often have the array transducers spaced much closer than one-half wavelength, usually only a few inches apart, in order to minimize the overall size of the sonar tow body. While a smaller tow body allows for ease in handling, such close transducer spacing produces areas (hot spots) between the transducers that are susceptible to cavitation production when the transducers are driven at high source levels. This cavitation damages the transducer surfaces over time, and the cavitation bubbles block the transmitted sound, thereby degrading the transmitted signal. One cavitation reduction solution that has been employed previously is to accept an undesirable reduction of the acoustic pressure (and hence, the source level of the operating array) with a corresponding decrease in sonar system performance. Another approach that has been tried is to fill in the gaps between closely spaced transducers with a rho-c rubber device thereby eliminating the presence of seawater between the hot spots. Such a solution however is complicated to design and relatively high in cost to construct.
What is needed is a low cost, simple-to-construct design for preventing cavitation from occurring between closely spaced transducers in a sonar array, even when the array is operated at high source levels.